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Article

Photochemical and Structural Studies on Cyclic Peptide Models

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Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4032 Debrecen, Egyetem tér 1, Hungary
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Institute of Chemistry, Department of Organic Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, 112. P.O. Box 32, Hungary
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Chemie Ltd., H-1022 Budapest, Herman Ottó út 15, Hungary
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Department of Analytical Chemistry, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest 112, P.O. Box 32, Hungary
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Department of Biophysics and Radiation Biology, Semmelweis University Budapest, H-1428 Budapest, P.O. Box 2, Hungary
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Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary
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Authors to whom correspondence should be addressed.
Molecules 2018, 23(9), 2196; https://doi.org/10.3390/molecules23092196
Received: 19 July 2018 / Revised: 24 August 2018 / Accepted: 26 August 2018 / Published: 30 August 2018
Ultra-violet (UV) irradiation has a significant impact on the structure and function of proteins that is supposed to be in relationship with the tryptophan-mediated photolysis of disulfide bonds. To investigate the correlation between the photoexcitation of Trp residues in polypeptides and the associated reduction of disulfide bridges, a series of small, cyclic oligopeptide models were analyzed in this work. Average distances between the aromatic side chains and the disulfide bridge were determined following molecular mechanics (MM) geometry optimizations. In this way, the possibility of cation–π interactions was also investigated. Molecular mechanics calculations revealed that the shortest distance between the side chain of the Trp residues and the disulfide bridge is approximately 5 Å in the cyclic pentapeptide models. Based on this, three tryptophan-containing cyclopeptide models were synthesized and analyzed by nuclear magnetic resonance (NMR) spectroscopy. Experimental data and detailed molecular dynamics (MD) simulations were in good agreement with MM geometry calculations. Selected model peptides were subjected to photolytic degradation to study the correlation of structural features and the photolytic cleavage of disulfide bonds in solution. Formation of free sulfhydryl groups upon illumination with near UV light was monitored by fluorescence spectroscopy after chemical derivatization with 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) and mass spectrometry. Liquid cromatography-mass spectrometry (LC-MS) measurements indicated the presence of multiple photooxidation products (e.g., dimers, multimers and other oxidated products), suggesting that besides the photolysis of disulfide bonds secondary photolytic processes take place. View Full-Text
Keywords: cyclopeptides; UV irradiation; photolysis; disulfide bridges; NMR; MD cyclopeptides; UV irradiation; photolysis; disulfide bridges; NMR; MD
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MDPI and ACS Style

Nagy, T.M.; Knapp, K.; Illyés, E.; Timári, I.; Schlosser, G.; Csík, G.; Borics, A.; Majer, Z.; Kövér, K.E. Photochemical and Structural Studies on Cyclic Peptide Models. Molecules 2018, 23, 2196. https://doi.org/10.3390/molecules23092196

AMA Style

Nagy TM, Knapp K, Illyés E, Timári I, Schlosser G, Csík G, Borics A, Majer Z, Kövér KE. Photochemical and Structural Studies on Cyclic Peptide Models. Molecules. 2018; 23(9):2196. https://doi.org/10.3390/molecules23092196

Chicago/Turabian Style

Nagy, Tamás Milán, Krisztina Knapp, Eszter Illyés, István Timári, Gitta Schlosser, Gabriella Csík, Attila Borics, Zsuzsa Majer, and Katalin E. Kövér. 2018. "Photochemical and Structural Studies on Cyclic Peptide Models" Molecules 23, no. 9: 2196. https://doi.org/10.3390/molecules23092196

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